Inhibiting taste and odor in glycollic acid



Patented Apr. 15', 1947 INHIBITING TASTE AND- onon IN GLYCOLLIC ACIDHarry G. Hetherington, Charleston, W. Va., as-

signor to E. I. du Pont de Nemours &.Company, Wilmington, Del, acorporation of Delaware NoDrawing. Original application March 28,1942,

Divided and this application January 25, I945, Serial No. 574,634

Serial No. 436,712.

This invention relates to the processing of organic compounds and moreparticularly processing of such compounds to render them free fromforeign tastes and odors. This application is a division of S. N.436,712, H. C. Hetherington, filed March 28, 1942.

Within the past decade so-called stainless steels, generally alloysteels of high chromium content, have been extensively used in theprocessing of corrosive chemicals and especially in processing chemicalsto be used for comestible purposes and for use inv potable liquids. Theuse of these steels has also considerably facilitated the preparation ofC. P. products and in many instances it is found possible to prepare theproducts without the necessity of further purification which ordinarilyis required when processing is carried out in vessels constructed ofother metals. Certain processes, however, although they are conductedinthe presence of only mildly acidic reactants could not be carried outin the alloy steel vessels without imparting odor or taste to theproduct and in some instances much time consuming and costly clean-upprocesses were necessary to give acceptable finished products.

An object of the present invention is to provide a process for thetreatment of organic compounds in alloy steel to give stable productsfree from contaminating taste and odor. Another object is to provide aprocess for the treatment of mildly corrosive organic compounds, orsolutions of such nature, in high chromium-alloy steel vessels wherebythe products are obtained free from foreign taste and odor. Yet anotherobject is to provide a process for the preparation of organic compoundsfree from foreign odor or taste which compounds are processed instainless steel vessels while in the presence of inorganic acids such assulfuric acid, hydrochloric acid, and the like by effecting the processin the presence of polyvalent metals. Other objects and advantages ofthe invention will hereinafter appear.

It has been found that liquids can be processed and/or stored in alloysteel vessels and foreign taste and odor avoided even though theproducts or the reactants from which they are formed are corrosiveprovided the processing and/r storage in said vessels is conducted inthe presence of polyvalent metals such, for example, as manganese,bismuth, cobalt, iron, or especially copper.

The advantageous result is particularly marked for reactions in whichorganic or inorganic acids are present, such as sulfuric, hydrochloric,oxalic, benzoic, acetic, propionic, tartaric, hydroxyacetic 2 Claims.(01. 260-535) acids, etc., as reactants or catalysts or are pres entduring the recovery of the product from the reaction mixture containingsuch acids. In the preparation of (methoxymethoxy) ethanol from methylaland ethylene glycol, sulfuric acid is used as the catalyst.(Methoxymethoxy) ethanol is recovered directly by distillation from thereaction product and inasmuch as this compound is used where odors wouldbe objectionable, the distillation is conducted in an alloy steel still.If no polyvalent metal is present the product picks up undesirable odorsduringv the distillation while if there is present 0;0002% or more of apoly val'ent metal such as those given above or equivalentconcentrations of salts thereof, such as sulfate, acid sulfate,phosphate, chloride, acetate, hydroxyacetate, or the like, the(methoxymethoxy) ethanol is recovered substantially free from foreignodors.

Foreign odor and taste can beavoided in organic liquids generally bythis method, and it is intended that the term liquids include compoundswhich may be solids under normal conditions of temperature and pressurebut which are processed under liquid phase conditions. For example, inthis category are included hydroxyacetic acid and its esters,glycolides, tartaric acid and its esters, citric acid and the like.

The alloy steels referred to in this specification include particularlythose which contain a high percentage of chromium, i. e. up to in theorder of 30% chromium. For example, the wellknown alloy steel containing18% chromium, 8% nickel, and the remainder mostly iron with traces ofcarbon, manganese, sulfur, etc., is extensively used as a material forthe construction of reactant vessels; as well as steels containing astheir major constituent, other than iron, from 12 to 14% chromium. Saidalloy steels are espeially adapted for use in accord with the invenion.

The wide applicability of this method will be appreciated from thefollowing processes in which it has been found to be very effective.

Example 1.In the preparation of dimethoxyethyl adipate, a mixturecontaining adipic acid, ethylene glycol monomethyl ether, and sulfuricacid was processed in an alloy steel reaction still kettle having acomposition of approximately chromium 18%, molybdenum 2%, nickel 8%.There was recovered from the reaction mixture a wholly unacceptableproduct with a sulfurous acid Similarly the sulfurous odor contaminatingdiisobutyl adipate, dicyclohexyl adipate, and dimethoxyethyl sebacate,prepared by esterification in alloy steel vessels, was eliminated in thesame manner. 1

Example 2.A stainless steel storage tank having an approximatecomposition of chromium 18%, molybdenum 2%, nickel 8%, was used forstoring a. 90% formic acid solution at normal temperature, the productafter a short storage period was highly contaminated. It was found thatthe contamination could be completely avoided by adding 0.02% of copperas copper formate to the 90% formic acid solution prior to storage.

Example 3.In the preparation of isobutyl carbamate 0.003% of copper asbasic copper carbonate was added to a mixture consisting of 1047 partsof isobutanol and 156 parts of urea. The mixture was heated for severalhours at a temperature above 150 C. in a stainless steel apparatus ofwhich some of the internal surfaces were of the approximate compositiongiven in previous examples and others of similar chromium and nickelcomposition but containing no molybdenum. The product, following removalof unreacted isobutanol and urea, was entirely free of the objectionableforeign odor which it acquires during its preparation in the absence ofcopper.

Example 4.-A mixture containing 354.6 parts of ethylene glycol, 311.6parts of a methylalmethanol azeotrope (containing 92% methylal), twoparts sulfuric acid, and 0.0075% copper which was added as coppersulfate, was refluxed for six hours in a stainless steel still, thekettle of which was of 18Cr-8Ni-2Mo composition and the heating coils,column and other parts of unmodified 188 composition. The reactionproduct was then distilled, yielding a, (methoxymethoxy) ethanol(CH3OCH2OCH2CH2OH) fraction which was not only free from foreign tasteand odor but which in addition was thermally stable. In the 4 absence ofthe copper the product was thermally unstable and possessed a highlyobjectionable odor.

Example 5.In the preparation of hydroxyacetic acid 780 parts of methylhydroxyacetate was hydrolyzed with 820 parts of water in the presence of0.0016 part of copper. This hydrolysis, the removal of methanol bydistillation, the subsequent concentrating of the aqueous solution andthe final flash evaporation or remaining free water were all effected instainless steel equipment of the approximate 18 chrome 8 nickel type.The crystalline hydroxyacetic acid obtained was entirely free of theobjectionable odor which had characterized this product when made undersimilar conditions but in the absence of copper.

I claim:

1.A method of inhibiting the development of foreign taste and odor inhydroxyacetic acid when in contact with chrome-alloy steels, whichcomprises incorporating in hydroxyacetic acid at least 0.0002% of copperions based on the weight of the hydroxyacetic acid.

2. A method of inhibiting the development of foreign taste and odor inhydroxyacetic acid during its formation from an ester of the acid whichcomprises hydrolyzing an ester of hydroxyacetic acid to hydroxyaceticacid in an 18% chromium- 8% nickel alloy steel vessel, there beingpresent in solution at least 0.0002% copper.

HARRY C. I-IETHERING'I'ON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,152,852 Loder Apr. 4, 19391,999,403 Dreyfus Apr. 30, 1935 2,352,641 King July 4, 1944

